1. Field of the invention
The present invention builds on the work of Georges BAIKOFF, Bernard GARNIER and Yves MAIGRET, and is generally concerned with improving the sight of a person suffering from macular degeneration, that is to say degeneration of the macula lutea of the retina of one or both eyes.
2. Description of the prior art
In macular degeneration, which usually affects only persons aged more than 65 years, there is a drop in the activity of the rods in the area of the retina concerned and this has two results; where near sight is concerned it becomes impossible to read and where far sight is concerned the loss of clear vision makes walking difficult.
In brief, the result is some form of visual impairment.
A first proposal for improving the sight of persons suffering from macular degeneration was to place before the eye to be treated, rather than a single ophthalmic lens, an optical system comprising a plurality of such lenses, constituting a Galilean telescope, for example, adapted to magnify the image formed on the retina of the eye concerned and so to illuminate a maximum number of the rods thereof.
However, the image enlargement feasible with any such optical system is relatively moderate and, more importantly, although some degree of vision can be restored in this way this applies only to a limited field, minimizing the benefit of this solution.
In this type of optical system all the lenses remain external to the eye.
Furthermore, optical systems of this kind using a Galilean telescope system are heavy and bulky.
More recently there has been proposed an optical system using the eye itself.
Formulated in various ways, an optical system of this kind generally comprises a combination of two lenses, namely a high positive power ophthalmic lens placed before the eye to be treated and a high negative power intra-ocular lens implanted in the eye in place of its crystalline lens.
The intra-ocular lens may be implanted in the posterior chamber of the eye, for example.
Alternatively, it may be planted in the anterior chamber of the eye.
In either case, the image magnification achieved with an optical system of this kind can be very much greater than that obtained with an optical system external to the eye and the corresponding field may also and advantageously be larger.
However, although consideration has been given to forming one of the lenses constituting this optical system, in practise the ophthalmic lens disposed before the eye, with an aspherical surface of revolution, there usually remain non-negligible aberrations in such optical systems, especially when the intra-ocular lens is implanted in the anterior chamber of the eye, both to facilitate the surgery required and to enable further intervention at a later stage. The inevitable result of this is some degradation of the quality of the image obtained.
The present invention is based on the observation that it is possible to improve very significantly the quality of the image by providing an aspherical surface of revolution on both the lenses constituting an optical system of this kind.